#22 #44 Article reviews and migration

Moved articles from the blog & reviewed them ("Pages & menus", "Widgets", "Working with permissions").

I have splitted "Adding pages & menu items" into separate guides. I have put it in a new category name "User Interface" (named can be changed):

![capture d ecran 2014-12-09 a 17 43 16](https://cloud.githubusercontent.com/assets/720328/5352437/e91a0cf6-7fca-11e4-8c3b-b37a0cfdb6f4.png)

I have moved "Working with Piwik's UI" in this category and renamed it to "Javascript and CSS". I found the previous name very confusing as we didn't know what it contained. The direction I'm going more and more is have very simple guides and have them explicit on their content (Pages, Menus, Widgets, Javascript & CSS…). I find navigation much easier with shorter and common names as we can get a better overview.

I have done something similar when migrating the blog article "Working with permissions": I named it "Permissions" and put it in a new "Security" category. The old "Security" guide is now "Security best practices".